Solved

Can you prove to me wiht some documents??

Posted on 2004-04-14
6
234 Views
Last Modified: 2010-04-01
Hi there, i have some "Debate" so call with some peoples regarding this issues. I or we are just hope to knw the truth.. please procide me some prove or document to support your point.

This is javaBean

abc.java
=======

import java.sql.*;
import java.io.*;
import java.math.*;


we are arguing that if we put the code like this (with .*) , it's will somehow "consume" our memory. Because it'll load all the java.sql's API into our program althouge we didnt use that.

and some say it will not affect at all. Because the Java is smart enough to clean or only load those package that the is used below the code.

So, which version is correct? Will it consume or not?

I am planned to do soething like

System.getMemory .. or something to see the different.. do you think i can do such?

Please provide me some URL so that we can read better...

tahnk you.

0
Comment
Question by:kuching
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 3
6 Comments
 
LVL 7

Expert Comment

by:searlas
ID: 10822125
The .* is interpreted at *compile time*, not at runtime.  The Java compiler will include all necessary references in a compiled class file, and no unnecessary ones.

All you have to do is check the size of the compiled class file:
import java.util.Date;
public class UtilDate {
    public static void main(String args[]) {
        System.out.println(new Date());
    }
}


-rwxrwxrwx    1 searlas  mkgroup-      434 Apr 14 12:03 UtilDate.class

import java.util.*;
public class UtilDate {
    public static void main(String args[]) {
        System.out.println(new Date());
    }
}

-rwxrwxrwx    1 searlas  mkgroup-      434 Apr 14 12:04 UtilDate.class
0
 
LVL 7

Expert Comment

by:searlas
ID: 10822132
And for completeness, not using an import at all:

public class UtilDate {
    public static void main(String args[]) {
        System.out.println(new java.util.Date());
    }
}

-rwxrwxrwx    1 searlas  mkgroup-      434 Apr 14 12:06 UtilDate.class
0
 
LVL 7

Accepted Solution

by:
searlas earned 75 total points
ID: 10822208
As a document reference, the class file spec should do:
http://java.sun.com/docs/books/vmspec/2nd-edition/html/ClassFile.doc.html

Note the structure of a class file - it contains no references to import statements at all.  Reading the document in more depth should satisfy you that this is indeed the case.
ClassFile {
    u4 magic;
    u2 minor_version;
    u2 major_version;
    u2 constant_pool_count;
    cp_info constant_pool[constant_pool_count-1];
    u2 access_flags;
    u2 this_class;
    u2 super_class;
    u2 interfaces_count;
    u2 interfaces[interfaces_count];
    u2 fields_count;
    field_info fields[fields_count];
    u2 methods_count;
    method_info methods[methods_count];
    u2 attributes_count;
    attribute_info attributes[attributes_count];
    }
0
 
LVL 4

Assisted Solution

by:john-at-7fff
john-at-7fff earned 75 total points
ID: 10827376
Here's a short and sweet answer: It will not consume memory in your running program.

So import foo.* all you want!!

http://www.javaperformancetuning.com/news/qotm031.shtml

0

Featured Post

Free Tool: ZipGrep

ZipGrep is a utility that can list and search zip (.war, .ear, .jar, etc) archives for text patterns, without the need to extract the archive's contents.

One of a set of tools we're offering as a way to say thank you for being a part of the community.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Originally, this post was published on Monitis Blog, you can check it here . In business circles, we sometimes hear that today is the “age of the customer.” And so it is. Thanks to the enormous advances over the past few years in consumer techno…
The recent Petya-like ransomware attack served a big blow to hundreds of banks, corporations and government offices The Acronis blog takes a closer look at this damaging worm to see what’s behind it – and offers up tips on how you can safeguard your…
In this video, viewers will be given step by step instructions on adjusting mouse, pointer and cursor visibility in Microsoft Windows 10. The video seeks to educate those who are struggling with the new Windows 10 Graphical User Interface. Change Cu…
In this video you will find out how to export Office 365 mailboxes using the built in eDiscovery tool. Bear in mind that although this method might be useful in some cases, using PST files as Office 365 backup is troublesome in a long run (more on t…

617 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question